Spectrophotometer antibacklash reduction drive



Sept. 12, 1944. Q W PlNEQ l2,358,097

SPECTROPHOTOMETER ANTIBACKLASH REDUCTION'DRIYE Filed April 29, 1942 :5 sheets-sheet 1 v v INVENTOR O/P/P//v Wfffa/w//vf-O,

O. W. PINEO sept. 12, 1944.

SPECTROPHOTOMETER ANTIBACKLSH REDUCTION DRIVE Filed April 29, 1942 ,5 Sheets-Sheet 2 1N VEN TOR.

sept. 12, 1944.

o. w. PINO SPECTROPHOTOMETER ANTIBACKLASH REDUCTION DRIVE Filed April 29,

1942 5 Sheets-Sheet 5 INV ENTOR.

into contact with the inner'periphery of the cupI The disc I4 is provided with two lugs I6 Awhich bolt into a forked arm I'I pivoted on a pin 20 carried by a rocking block 2I which in turn rocks on two points 22 engaging hollows 23 on the framework of the spectrophotometer. A spring I8 presses the arm II tightly against the rocking block 2| and keeps the pivot 20 inthe depression I9 of the arm. The connectionpermits` the arm II to move up and down and alsov to move sideways.

Whenthe motor 4 starts to turn the lshaft 5, this transmits the motion by friction to the disc 6 which inturn `carries disc III around with it. The latter rotates about the hub of .the disc I4 and the'tension of the 'springs I2 tends to rotate the disc III about the pin I. The disc I4 is forced tomove also and is kept in contact with the periphery of the cup 24 at a point approximately 90 from the location ofthe pin 9. Because of the arm I'I,.disc I4 cannot rotate butV moves up and down, its center describing a circle.

The proportion' of the clearances so that-the disc I4 contacts the cup 24'at approximately 90 from the pin 9 represents some advantages because pullof the springs actsmore or less at right angles to the periphery of the cup 24 at point of contact. As a result there is but little if any'wedging action and hence the degree of friction is substantially the samein either direction of rotation. It is thus possible bychoosing suitable spring dimension to have a frictional vcontact which will not slip under ordinary operation but rwhich is notso great as to prevent turn-.

ing the cup 24 manually. This permits moving the cup 24' and vits shaft for purposes of shifting cams or `restarting a measuring cycle without disconnecting any portions of the drive and even without requiring themotor` 44 to be stopped. This is of considerable advantagein a spectrophotometerA drive. On the other hand, where the a second quarter of a revolution, 8D the position after a third quarter of a revolution, and 8E after one revolution has been completed.

It will be noticed that the disc I4 and the :up 24 are always in rolling contact but no slippage results because the springs I2 press the disc I4 and cup 24 .together along their lineof Contact.

speed reducer is to be used under such circumstances'that it never has to be slipped by manualr operation and always turns'in4k the same direction, it is advantageous to locate the springs so that the contact of the disc I4 withthe cup 24 will take place at a point not far removed from 180f'from the pin 9. This ywill result in a very strong wedgingfaction in one direction of drive and comparatively light spring will permit a drive that will not slip from'under fairly heavyloads and in'cases where heavyloads are encountered, and nov slippage is desired, such modification is of advantage. In general, the present invention is notlimited to a design in which lthe disc I4 encounters the periphery of cupv 24 at any, particular point. i

Figs. `8AE show in diagrammatic forma cycle of rotation. "The position of the pin 9 is shown on thevdiagrarn in dotted lines, Ithe springs I2 have forced the disc I4 into contact with the cup 24 at the point. shown. As the disc 6 rotates a quarter of a revolution to the position shown in Fig. 8B.' the point of contact between the disc I4 and the -cup 24 has shiftedand hence the rotation of the disc 24 isthe smalliarc shown between the arrows at the left and amounts to the difference kin periphery between the cup 24 and A high degree of reduction is obtained without any backlash whatsoever. Also, since the members of the drive are in rolling contact, friction loss is reduced'to a minimum.

The above description illustrates the operation of the speedv reduceras such. In addition, in the case of a flickering beam spectrophotometer such as is shown in Fig. 1, it is sometimes desirable to provide for a cam changing means in the hous- -ing 2, and for this purpose the shaft I'I can be moved axially to bring successively different cams inv contact with the push rod 3. This is possible as the disc `6 can move alongthe shaft 5 for a reasonable distance because of the fact that the arm I1 canA pivot about the pin 20.1 Where provision for smallaxial movement is not'necessary, this second 'degree of motion of the arm I1 may be eliminated and its suspension at the end can be somewhat simplified. In the present invention the'cam shifting, device for a spectrophotometer is not claimed as this forms the subject matter of 'my copending application Serial No. 441,029, filed Apri129, 1942. Its structural de. tails form no part of the present invention.

`It will be noted that a. double reduction is effected, first thereduction from the shaft 5 tothe disc 6, and secondly the reduction in speed between the disc E and the cup 24. Where as great a speed reduction is not necessary'or desired, the disc 6 may be ydriven directly or if desired a plurality of reduction drives as shown in the present invention may be arrangedin series. In other lwords, shaft I can drive the driving disc of a second speed reducer. In this manner enormous reductions can be obtained without backlashand quiring but little power such as the spectro-v photometer drives in connection with which it haspbeen specifically described, but it may also be used where greater amounts of power are necessary. It is in the former drives, however,

that its greatest utility is achieved because drives l which are to transmit high torque can be arranged so there is less backlash than in drives where the torque transmitted is relatively small. However,

,the application of the speed reducer of the present n invention is not intended to be limited to any particular class of devices.

Essentially the arm I'I and its attachment to the disc I4 is a device which will permit small movements'of the center of thedisc in circular or elliptical paths but will prevent rotation. A

pivot arm, particularly Where the length of thel arm is large in comparisonwith the amount of movement of the center of the disc, represents a the disc u. Fig'scsnows the conditions 'after 7 `very. simple structure, particularly for drives where small torque is tobe transmitted. It should be understood, however, that any, other means which will restrict the degree of motion of disc I4 may be used. f

I claim: f o

1. A speed reducer comprising Ia cup-shaped driven member keyedto a driven shaft, said member having a cylindrical inner surface, a circular driving member having its center of rotation coincident with the driven shaft, two disc. members.

2,358,097 c 3 the rst one being positioned within the cupa pin adjacent to the periphery of the driving j shapeddriven member and having a circumfermember, spring means connectingv the second ence somewhat smaller than the internal diamedisc and the driving member at a point t0 cause ter of the driven member, said disc being prothe second disc to tend t `turn about the pin as vided with a central hollow hub, the second disc 5 a pivot, the first disc being provided with two being journaled on said hub and being pivoted on oppositely positioned lugs on its periphery exa pin adjacent to the periphery of the driving tending beyond the cup-shapeddriven member member, spring means connecting the second disc and ending in pins paralle1 to the plane of the and the driving member at a point to cause the disc, a member forked at one end of great length second disc to tend to turn about the pin as a 10 in comparison to the diameter of the rst disc pivot, and means associated with the first disc to pivoted on said pins and extending in 'a plane permit gyrations thereof of limited extent of the substantially parallel to the plane of the disc, the plane thereof but preventing it from rotation. other end being pivoted s o that the forked end is 2. A speed reducer comprising a cup-shaped capable of limited movement both parallel to the driven member rigidly attached to a driven shaft, l5.I plane 0f the fllSt disc and at right angles thereto, said member having a cylindrical inner surface, a driving motor having elongated shaft parallel a circular driving member having its center of to the driven shaft of the speed reducer and in rotation coincident with the driven shaft, two disc fIiCtOIlal COIlaCl With the periphery .0f the Cilmembers, the nrst one being positioned within the cular driving member, the elements of the speed cup-shaped driven member and having a circum- 2o reducer With the exception of the unforked end ference somewhat smaller than the internal diof the forked element being' Capable of limited ameter of the driven memben'said disc being proaxial movement. vided with a central hollow hub, the second disc ORRIN WESTON PINEO. being journaled on said hub and being pivoted on 

